The present invention relates to gas dryers for removing the moisture from a sample gas stream, and is directed more particularly to a gas dryer cartridge having a liquid collecting chamber for receiving and retaining the liquid produced during the operation of the dryer.
Under circumstances where measurements are to be made on a moisture-laden gas, such as human breath, it is frequently desirable to first remove the water therefrom. This is because the failure to remove such water can significantly affect the accuracy of measurements made on the gas as, for example, by condensing on the interior surfaces of the instrument. Depending on the type of instrument, the presence of water may also be objectionable because of its activity as an interfering component.
Prior to the present invention, gas dryers have typically included a generally cylindrical housing having an inlet and an outlet at opposite ends thereof. Within the housing was located a body of a desiccating material, such as calcium chloride, which was held in place by upstream and downstream retaining elements, such as metal screens. While such dryers perform satisfactorily under conditions in which their desiccants are not allowed to exceed their maximum water absorbing capacities, they can adversely affect the operation of an instrument with which they are used, if those water absorbing capacities are exceeded. If, for example, the length of a series of measurements, or inattention on the part of an operator causes a dryer cartridge to be used too long, the desiccant will exceed its maximum capacity. When this occurs, the desiccant will begin to liquefy, forming a salt solution which can escape from the desiccant. This salt solution can, in turn, be swept up by the gas stream and carried into the associated instrument. Should such a condition occur near the end of a long sequence of measurements, it can result in the non-usability of the data taken during the entire sequence. In an extreme case, in which a large part of the desiccant is liquefied, substantial quantities of this liquid may be drawn into the instrument causing clogging, corrosion or other serious damage.